Thermal overload circuit breaker



Feb. 25, 1958 J. ELLENBERGER 2,824,932

THERMAL ovERLoAD CIRCUIT BREAKER Filed July 15, 1955 .WWA/70K jqjg E//energer United States Patent @thee o 2,824,932 Patented Feb. 25, 1958THERMAL OVERLOAD CIRCUIT BREAKER `akob Ellenberger, Altdorf, nearNnrnberg, Germany, assignor to Ellenberger & Poensgen G. m. b. d., acorporation of Germany Application July 15, 1955, Serial No. 522,305 9Claims. (Cl. 20G- 116) The present invention relates to a thermaloverload circuit breaker, and more particularly to further improvementsin the thermal overload circuit breaker as described and illustrated inmy prior copending application Serial No. 222,473, now Patent No.2,767,281.

That prior application describes and shows a thermal overload or excesscurrent circuit breaker which is provided with a contact bridge having apush button which when depressed against the force of a disconnecting orrelease spring places the contact bridge into its operative orcontact-making position in which it is held by means of a projectingcontact which is mounted on the free end of a bimetallic strip which isheated by the current which the circuit breaker is intended to control.In this operative position, the contact bridge also forms the connectionto a second contact. If a current passes through the bimetallic strip,the projecting contact disengages from and releases the contact bridgewhich can then be moved by the disconnecting spring into thecircuit-breaking position in which the electrical connection will beinterrupted both between the contact bridge and the bimetallic strip, aswell as between the contact bridge and the second contact.

It is an object of the present invention to provide an overload circuitbreaker of the type as described which, considering its highcircuit-breaking eiciency, is of very simple construction and smalldimensions, and which is further provided with means for controlling anauxiliary electric circuit so that the latter will be closed when thecircuit breaker is in its disengaged or released position, suchauxiliary circuit serving to indicate or record such released positionof the circuit breaker at a point remote from the place of installationof the circuit breaker.

Another object of the present invention is to provide a circuit breakerof the type as described which substantially retains the same smalldimensions and mechanical simplicity as if Such additional mechanismwere not provided therein.

A feature of the invention for attaining the latter object consists inloosely mounting on the movable element which also forms the support ofthe contact bridge and is operated by a push button, 'a contact disk soas to be insulated from the Contact bridge by a suitable insulating diskor the like. Such contact disk then forms a secondary contact bridge foran auxiliary electric circuit which is closed under the pressure of thedisconnecting or release spring of the circuit breaker when the latteris in its current-breaking position.

According to the invention, the stationary contacts for the auxiliarycircuit are formed by two Istationary L- shaped contact strips, thelonger arms of which formthe longitudinal sides of the circuit breakerproper and carry soldering terminals at their lower ends which are to beconnected to the auxiliary circuit, while their short, substantiallyhorizontal arms which face each other form the counter-contacts whichare to be bridged by the contact disk so as to close the auxiliarycircuit when the circuit breaker is in its released position. Forincreasing the stability of these contact strips, as well as of theentire CTI lil

circuit breaker, they may also be interconnected by means of aninsulating member which connects the short arms of the contact stripswith each other so that the contact strips with the insulating memberform a framelike unit. This insulating member also forms a guidingelement for supporting and guiding a switch-on button, which isconnected to the contact bridge, as well as a release button which actsupon an inclined surface on the movable end of the bimetallic strip.

It is a further object of the present invention to provide the circuitbreaker with a measuring contact which, although safely hidden toprevent accidental injury to the operator, is easily accessible vfromthe outside of the circuit breaker, such measuring contact permittingthe resistance of the heating coil on the bimetallic strip or thecontact resistance of the switch contacts on the contact bridge to bemeasured even though the circuit breaker has been installed in a wall ormachine and its inner parts are thus not accessible from the outside.

Another object of the present invention is to provide the circuitbreaker with suitable means for holding the Contact bridge in a positionintermediate the contact-making and contact-breaking position, in whichintermediate position both electric circuits, that is, the main circuitas well as the auxiliary circuit are interrupted.

A feature for attaining this latter object of the invention consists inproviding a block of insulating material to support the main contactbridge and to provide such insulating block with a suitable angularnotch or tooth which i is adapted to cooperate with the lockingprojection on the movable end of the bimetallic strip. This angularnotch or tooth is preferably provided on the insulating block at a pointintermediate the fully engaged and fully released positions of thecontact bridge so that, when the switch-on button is partly depressed,the locking projection on the bimetallic strip will engage with suchintermediate notch and hold the circuit breaker in a position in whichneither the main contact bridge closes the main circuit nor theauxiliary contact bridge closes the auxiliary circuit.

Still another object of the invention is to provide means for preventingan accidental locking of the circuit breaker in such intermediateposition. This object may be attained by tapering-down the outer facesof the notch or tooth on the insulating block both above `and below thelocking surface thereof, so that when the projection on the bimetallicstrip bends away from and releases the contact bridge, it will notaccidentally engage the intermediate notch but slide past the same andrelease the insulating block entirely to assure the closing of theauxiliary current.

Additional features and advantages of the present invention will becomeapparent from the following detailed description thereof particularlywhen read in connection with the accompanying drawings, in which:

Fig. 1 shows a longitudinal section through the circuit breakeraccording to the invention;

Fig. 2 is a plan view thereof, with the housing of the circuit breaker,however, only being indicated in dotand-dash lines;

Fig. 3 is an enlarged detail view, showing the contact bridge arrestedin the intermediate position; while Y Fig. 4 shows the contact bridge inthe fully released position so as to close the auxiliary electriccircuit.

Referring to the drawings, the housing 1 of insulating material which isopen at its lower end contains an insulating member 2 preferably ofceramic material on which the two Contact terminals 3 and 4 are securedto which an auxiliary electric circuit is to be connected, as well asthe two inner terminals 5 and 6 leading to the main circuit. Each of thetwo connecting strips 3 and 4 forms a substantially L-shaped supportingmember ou the shorterupp'er arms ofwhich a plate 7 of insulatingmaterial is secured which is' provided with a central aperture withinwhich the switch-on button t5V is slideably guided which a coil spring24 tends to hold in an elevated position. The' cohtaet member 3 and theinsulating plate '7 are furtherV provided with coaxial bores foradditionally supporting andV guidinga release button 9'which isslideablymounted in a suitable aperture in the cover plate which preferably formsan integral part of the housing 1. The button 9 is provided with anarrow central bore extending entirely therethrough, and in said bore ametallic pin 29 is firmly secured which has at its lower end a smoothlyrounded contact head. As shown in Fig. 1,'.the pin 29 does, however, notextend entirely through the bore in the bntton9 but terminates at apoint below the upper surface thereof which is spaced a sutiicientdistance from such upper surface so that the linger' of the operatorwhen depressing the release button 9 cannot possibly come into contactwith the pin 29 and receive an electricshock. A coil spring 23 aroundthe button 9 tends to maintain the button in a raised position in whichit is normally held by the projecting contact head of the metallic pin29 abutting against the lower surface of the short arm of the contactmember 3.

The central switch-on button 8 is provided atzits lower end with apin-shaped threaded portion of reduced diameter which is screwed into aninsulating block 13 which carries on its upper surface an annularcontact member 12 with a downwardly extending prong 12' which is adaptedto be iirrnly engaged by two contact springs 22 when the switch-onbutton S is in its fully depressed position. On its lower surface, theinsulating block 13 also carries a guide member 14.which is likewisescrewed to the threaded extension of the button 8 and laterally guidedwithin a vertical slot 15 of an elongated rail 16 which has a pair ofprongs at its upper end inserted into a pair of notches 17 in the upperhorizontal portion of the contact member 4. Likewise screwed on thethreaded stern of the button A3 and so as to overlie the annular contactmember 12 is an insulating disk or sleeve 11. Intermediate the stemportion and the main cylindrical portion of the button member S is aneck portion on which a round contact disk 1d is loosely mounted andresting on the insulating disk 11, so that, when the button 8 is in itsfully released upward position, such contact disk 10 connects the twoL-shaped contacts 3 and 4, the lower ends of which are connected to theVauxiliary current circuit.

Gn the left side, as shown in the drawings, the main terminal 5 isrigidly secured by a screw 21 to one end of a birnetallic spring strip19, which carries adjacent its outwardly bent upper end a contact 18which has an inwardly projecting iinger thereon which, when the pushbutton S is fully depressed against the action of the 4spring 24,engages the upperV surface of the annular contact member 12thus closingthe main circuit with the current then ilowing from the terminal 5through the screw 21, f

the bimetailic strip 19, the annular Contact member 12, its prong 12',the two contact springs 22, and the screw 23 to the other main terminal6. As shown in Fig. l, the bimetallic strip 19 is also provided with aheating coil 241 which is electrically insulatedtherefrom along itslength and the ends of which are connected thereto either in parallel orin series.

Approximately half-way intermediate the upper. surface of the annularcontact member 12 and the lower end of the insulating block 26, thelatter is provided on the left side thereof, as seen in the drawings,with a notch 25 into which the inwardly projecting finger of the contact18 is first adapted to engage when the push button 3 is being depressed.if, at such time, the push button 8 Vis no further depressed, contact 1%arrests the insulating block 13, as well asthe annular contact member12,- and the contact disk 1t) in an intermediate position, wherein theContact'member 12 is disconnectedV from the contacts 18 and 22, and thecontact disk Iltl is disconnected from the contact members 4 and 5 sothat both the main current circuit, as well as the auxiliary currentcircuit, are interrupted.

To assure a smooth operation of the circuit breaker and a gradual andsecure locking action of the contact 18 with both the notch 25 and theupper surface of the contact member 12, respectively, the left outerface of the insulating block is tapered off so as to form a surfacewhich is inclined at a suitable angle 27 relative to the perpendicular.Thus, when push button 8 is being depressed, the inclined surface 26slides along the inclined face ofthe contact 18, thereby bending backthe bimetallc strip 19 against its spring force until the horizontalsurface of'notch 25 reaches the level of the lower surface of theprojecting linger of contact 13 and the latter can snap into notch 25and hold the insulating block 13 in the intermediate position in whichboth contact members 12 and 10 are disconnected-from their respectivecounter-contacts so that neither the main nor auxiliary currents areable to flow through the circuit breaker.

When the push button 8 is'then further depressed, the

inclined face 26' of notch 26 slides along the face or tip of contactnger 1S, thereby again bending back the bimetal strip 19 against its ownspring action until the upper surface of contact member 12 reaches thelevel of the lower surface of contact finger 13 and the latter is ableto snap into full engagement with contact member 12. Since at the sametime, the contact prong 12 of contact member 12 has been engaged by thetwo contact springs22 the main current circuit is closed as previouslydescribed.

The release of the circuit breaker is effectedy either automatically bythe tendency of the bimetallic strip 19 to bend when heated, or manuallywhen the release button 9 is being depressed. If the current passingthrough the bimetallic strip 19 and/or the heating coil 20 should becomeexcessive and the bimetallic strip thus be heatedv either directly orindirectly, it will bend outwardly" so that the contact finger 18 willdisengage from contact member 12. Simultaneously, therewith, the strongspring 24 will pull the insulating block 13 quickly upwardly andtherebywithdraw the contact prong 12 from the contact springs 22, thussuddenly interrupting the main circuit.

By the provision of the release button 9, the'circuit breaker may alsofunction as a manually operated switch'. When the button 9 is beingdepressed, its smoothly rounded head will engage with the outwardly bentupper end of the bimetallic strip 19 and thereby bend the stripoutwardly, thereby disengaging the contact finger 18 from the contactmember 12 so that the flow of current will be interrupted and the spring24 can pull the insulating block with the contact member 12 in an upwarddirection. By tapering'the left face of the insulating block 13inwardly, an accidental engagementof the contact n'ger'lS with the notch25 during the release movement will. be prevented regardless of whetherthe bimetallic spring strip 19 bends of its own accord, that is, throughbeing heatedl by an excess current, or by being manually disengaged fromcontact member 12 by the release button 9 since the outer tip of thenotch 25 is located further inward from the tip of the contact iingerllSthan the outer edge` of the contact member 12. Thus, in either eventtl1econtact member 12 when released will move fully upwardly so that thecontact disk 10 will always interconnect the two contact members 3 and 4and close'the auxiliary circuit which may lead to a suitable indicatingrecording or alarm device which may be located at any suitable pointremote from' the circuit breaker.

ual releaseof the circuit breaker. Y

By the provision of the central aperture in the release button 9, it isalso possible, even though the circuit breaker is installed in a closedapparatus or machine to measure the resistance of the heating coil 20 orthe contact resistance, respectively, by inserting a thin measuring pininto such central aperture of the depressed button 9 and into contactwith the metallic pin 29, and by connecting the other terminal of themeasuring instrument either to the terminal or to the terminal 6,respectively. The first measuring circuit extends through the pin 29,the contact 18, and the heating coil to the terminal S, while the secondmeasuring circuit extends through the pin 29, contacts 18, 12, 12', and22 to the terminal 6.

Although my invention has been illustrated and described with referenceto the preferred embodiments thereof I wish to have it understood thatit is in no way limited to the details of such embodiments or to thespecific examples described, but is capable of numerous modificationswithin the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1s:

1. A thermal overload circuit breaker contact member in the form of acontact bridge, a resilient bimetallic strip, one end of said stripbeing fixedly mounted and adapted to be connected to one line of anelectric operating circuit, the other end of said strip be ing freelymovable and having a contact finger thereon, said contact linger beingadapted to engage with said contact member, said bimetallic strip whenheated being adapted to bend and thereby disengage said contact fingerfrom said contact member, a stationary contact element adapted to beconnected with said contact member when said contact finger is engagedwith said contact member, said contact finger being electricallyconnected solely with the contact member if the contact member iselectrically connected with the said stationary contact element, saidcontact element adapted to be connected to the other line of saidoperating circuit, means for mounting said contact member and for movingthe same from a first position in which an auxiliary circuit is closedinto a second position wherein said contact member engages with andforms an electrical connection to said contact finger and said contactelement so as to close said operating circuit, the said contact memberbeing rigidly connected with the said mounting means, resilient meansengaging against said mounting means and tending to maintain saidcontact member in said first position and to return the same to saidfirst position when said contact member is disengaged from said contactfinger, a second contact member rigidly mounted on said mounting meansand electrically insulated from said first contact member, and a pair ofcontacts adapted to be connected to the auxiliary current circuit, saidsecond contact member being adapted to interconnect said pair ofcontacts when said mounting means are in said first position.

2. A thermal overload circuit breaker comprising a housing having acover, an operating element having a push button at least partlyprojecting outwardly from said cover and a lower portion extending intosaid housing, said element being mounted in said cover so as to beslidable in an axial direction, a spring tending to maintain saidelement in a raised position relative to said housing and cover, a firstcontact member mounted on said lower portion, a stationary contact onsaid housing and adapted to be connected to one line of an electricoperating current, a resilient bimetallic strip having a lower endfixedly mounted on said housing and adapted to be connected to thesecond line of said operating circomprising a.

cuit, and an upper end being freely movable and having a contact fingerthereon, said contact member when depressed by said push button and saidoperating element being electrically connected with said stationarycontact, and adapted to engage with said contact finger on saidbimetallic strip and to be locked thereby in such depressed position,said bimetallic strip when heated being adaptedj to bend and therebydisengage said contact finger from said contact member to release thesame to be returned by the action of said spring to said raised positionand disengage from said stationary contact, a second contact membermounted on said lower portion of said operating element and electricallyinsulated from said first contact member, and a pair of contacts adaptedto be connected to an auxiliary current circuit, said second contactmember being adapted to interconnect said pair of contacts when saidoperating element is in its raised position.

3. A thermal overload circuit breaker as defined in claim 2, whereinsaid second contact member comprises a disk, said disk being looselymounted on said lower portion of said element, said pair of contactscomprising two stationary L-shaped contact arms having solderingterminals at their lower ends, the upper shorter parts of said contactstrips facing and being separated from each other and being adapted tobe electrically connected by said contact disk when said operatingcircuit is interrupted by said circuit breaker and said operatingelement is in its fully raised position.

4. A thermal overload circuit breaker as defined in claim 2, furthercomprising a release button slidably mounted in said cover, a springtending to maintain said release button in a raised position, saidbimetallic strip having an inclined upper end, said release button whenbeing depressed adapted to engage said inclined end so as to bend saidbimetallic strip and thereby disengage said contact finger from saidfirst contact member when said operating element is in its depressedposition so as to release the same to return to its raised position.

5. A thermal overload circuit breaker as defined in claim 2, whereinsaid release button has a small central bore extending therethrough, acontact pin secured within said bore and having a contact head at itslower end, the length of said contact pin wit-hin said bore beingshorter than the length of said bore so as to leave a free opening inthe upper end of said release button, said free opening being adapted topermit access of a measuring instrument to the upper end of said contactpin, said bimetallic strip having an upper inclined end, said contacthead, when depressed together with said release button being adapted toengage said inclined end so as to bend said bimetallic strip and therebydisengage said contact finger from said first contact member when saidoperating element is in its depressed position so as to release the sameto return to its raised position.

6. A thermal overload circuit breaker as defined in claim 3, wherein theupper shorter parts of said L-shaped contact arms are secured to andinterconnected by a plate of insulating material so that said contactarms with said insulating plate form a framelike structure, saidinsulating plate having an aperture therein, said operating elementbeing slidably guided within and supported by the wall of said aperture.

7. A thermal overload circuit breaker comprising a contact member, aresilient bimetallic strip, one end of said strip being fixedly mountedand adapted to be connected to one line of an electric operatingcircuit, the other end of said strip being freely movable and having acontact finger thereon, said contact finger being adapted to engage withsaid contact member, said bimetallic strip when heated being adapted tobend and thereby disengage said contact finger from said contact member,a stationary contact element adapted to be connected with said contactmember when said contact finger is engaged with said contact member,said contact element adapted to be connected to the other line of saidoperating circuit, means for mounting said contact member and for movingthe same from a first position into a second position wherein saidcontact member engages with and forms an electrical connection to saidcontact finger and said contact element so as to close said operatingcircuit, resilient means tending to maintain said contact memberintsa'id'ffirst-'position and to return the same to said''rstppsition'rwhensaid contact member isV disengaged froml saidlconta'ctfinger, a ysecond contact member mounted on` said mountingme'ans andelectrically insulated from said'rst contact member, and a pair ofcontacts adapted to* be connected to the auxiliary current circuit, saidsecondcontact member being adapted to interconnect said pair` of`contacts when said mounting means'are in said iirst. position, auinsulating member mounted on said mounting means,- said' insulatingmember having a notch therein', said contact inger being adapted toengage into said notch vof said'insulati'ng member when said mountingmeans' are being Vmoved'from-said first position toward' said secondposition to arrest said" insulating member, saidV mountingmeans,l andsaid iirst and second contact members in aposition intermediate saidfirst and second positions wherein said first and'second contact membersare spaced'from said Contact iinger, said contact element and said'pairof contacts.

8. A'thermaloverload circuit breaker as defined in L claim 2, further'comprising an insulatingmember mounted on said lower portion of said'operating element below said first and second contact members, saidinsulating member having a side wall facing said contact finger, saidside wall being'inwardly inclinedfrom the upper to the lower end thereofand having a tooth-shaped' notch in said inclined side wall, saidcontact finger on said bimetallic strip being adapted to engage intosaid notch in said insulating member when said push button andoperatingfelement are`depressed to an intermediate position betweensaidr raised and fully depressed positions,l

and'to arrest said insulatingV member, said operating ele! ment,'a'ndvsaid first and second contact members in a position wherein said firstand second contact members are spaced from said`contact iinger, saidstationary contact, and said pair of contacts.

9. A thermal overload circuit breaker as delined in claim 8, whereinsaid insulating member supports said iirst contact member, said firstcontact member comprising an L-shaped member, the shorter substantiallyhorizontal arm of said last member forming the contact which is adaptedto be engaged with said contact finger on said bim'etallic strip, thelonger arm Yextending through said insulating member and the free lowerend thereof forming a prong, said stationary contact having a pair ofco-operating-contact springs at its upper end and a soldering terminalat its lower end, said prong being adaptedto engage between said contactsprings when said irst contact member is in its fully depressedposition. Y

References Cited in the le of thispatent UNITED STATES PATENTS 2,044,449Rivers et ai; June 16, 1936 2,093,335 Moody Sept. 14,1937 2,284,756Meyer June 2,v 1942 2,625,624 Ingwersen Jan. 13, 1953 2,647,969 'MarcozAug. 4, 1953 FOREIGN PATENTS 794,535 France Dec. 12, 1935 928,149Francel May 26, 1947

